Sequence switching system in tracer control unit

ABSTRACT

The present invention is intended to make it possible to enlarge or reduce, as desired, a preset tracing range in a tracer control unit by actuation of a control switch (36) externally provided. To this end, according to the present invention, the tracer control unit is arranged so that it ignores a sequence changeover during actuation, that is, the ON state of the control switch (36) for inputting a sequence changeover signal and executes a sequence changeover which has been or is to be ignored when the operation of the control switch (36) is released, that is, turned OFF.

BACKGROUND OF THE INVENTION

The present invention relates to a sequence switching system in a tracercontrol unit with which it is possible to manually change the timing forswitching of a tracing sequence by means of a control switch externallyprovided.

Conventional tracer control units, in general, mechanically set atracing path, for example, a tracing range in the X-Y plane by means ofa limit switch, or by storing the machine position in a memory, and cuta workpiece within the set range while at the same time tracing a modelwith a stylus of the tracer head. It is difficult, however, toaccurately predetermine the tracing range. To get over this problem, asequence changeover system has heretofore been proposed which has acontrol switch externally provided for manually changing the switchingof a tracing sequence, and which permits, by pressing the controlswitch, a sequence changeover, for instance, from a tracing operation toa pick feed operation even if the stylus lies within a preset tracingrange. According to such a sequence, changeover system, a desiredtracing range is first set and then modified in succession during theactual tracing operation.

With the conventional sequence changeover system, however, the sequencechangeover is possible only within the preset tracing range butimpossible outside it. This inevitably calls for a wide preset tracingrange, incurring an increase in the time for tracing.

SUMMARY OF THE INVENTION

The present invention has for its object to enable a manual change ofthe timing for a sequence changeover by actuation of an externallyprovided control switch, whether within or without a preset tracingrange.

The present invention is directed to a sequence switching system for atracer control unit which operates according to a tracing direction anda tracing speed based on signals from a tracer head tracing the modelsurface and performs tracer control, and which is provided with acontrol switch for inputting a sequence switching signal, a sequencechangeover ignore means for ignoring the current sequence changeoverduring the actuation of the control switch and a sequence changeoverexecute means for executing a sequence changeover which has been or isto be ignored when the operation of the control switch is released.Accordingly, when continuing the operation of the control switch, evenif the stylus goes beyond a preset tracing range, that is, even if alimit switch defining the tracing range is stepped on or the machineposition reaches the position stored in a memory that defines thetracing range, no sequence changeover takes place, and at the point oftime when the operation of the control switch is released, a sequencechangeover is carried out. Therefore, the sequence changeover can beachieved in a region outside the tracing range. Further, by once turningon the control switch within the tracing range and then turning off theswitch at a desired position within the tracing range, the sequencechangeover which is to be ignored is performed upon turning off of theswitch, so that it is also possible to change the timing for a sequencechangeover in the region within the tracing range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating the principal part of an exampleof a tracer control unit embodying the sequence switching system of thepresent invention;

FIG. 2 is a diagram showing an example of tracing operation data;

FIG. 3 is a diagram showing an example of a tracing mode;

FIG. 4 is an explanatory diagram of an example of a tracing path; and

FIG. 5 is a flowchart explanatory of operation.

DESCRIPTION OF PREFERRED EMBODIMENTS

In FIG. 1, a stylus 3 of a tracer head 2 makes contact with a model 1and is fed by an X-axis servo motor 4, a Y-axis servo motor 5 and aZ-axis servo motor 6. Based on displacement signals ε_(x), ε_(y) andε_(z) corresponding to displacement of the stylus 3, a displacementcombining circuit 7 outputs a composite displacement signal ε ##EQU1##and an indexing circuit 8 outputs displacement direction signals sin θand cos ε. The composite displacement signal ε is provided to an adder9, wherein a difference Δε is obtained between it and a referencedisplacement signal ε₀ from a D/A converter 10. Velocity operationcircuits 11 and 12 produce a normal velocity signal VN and a tangentialvelocity signal VT, respectively, and based on the displacementdirection signals sin θ and cos θ, a distribution circuit 13 produces avelocity command signal, which is applied to a gate circuit 14. Thevelocity command signal is provided to one of amplifying output circuits15 to 17 which is selected by the gate circuit 14, and a correspondingone of the servo motors 4 to 6 is driven corresponding to the velocitycommand signal, by which a cutter 18 and the tracer head 2 are fed asone body to cut a workpiece 19.

Data for defining a tracing operation is entered from a keyboard 20 orthe like and stored in a memory 23 which comprises a data memory part 21and a control program part 22. As the tracing operation proceeds, thedata is read out of the memory 23 and a tracing path is controlled inaccordance with the data. The input data may be such, for example, asshown in FIG. 2. Incidentally, such modes as shown in FIG. 3, forinstance, can be adopted as tracing modes.

Assuming that approach from a starting point A is directed to a point aand that tracing stroke limits LP and LN are X₁ and X₂, a pick feedvalue is P, a tracing end position LTE is Y₁ and an automatic returnposition LRP is Z₁, as depicted in FIG. 4, and in the case wherevelocity, direction and other data are entered to perform tracing via aroute a, b, c, . . . u, v and to return from the tracing end position Y₁to the position Z₁ based on automatic return data, control is effectedfollowing the flowchart shown in FIG. 5(a).

Upon pressing an approach button not shown, a processor 24 reads outdata on the approach axis, approach direction and approach speed fromthe memory 23 and provides a signal via a data output device 25 and amanual setting signal circuit 26 to the gate circuit 14 to activate theamplifying output circuit 15, bringing down the tracer head 2 and thecutter 18 by the Z-axis servo motor 6. The speed in this case can bedetermined by data F which is provided via the data output device 25 toa D/A converter 27.

Since the displacement signals ε_(x), ε_(y) are zero before the stylus 3is brought into contact with the model 1, the difference signal Δε isequal to the reference displacement signal ε₀. When the compositedisplacement signal becomes equal to the reference displacement signalε₀ after the stylus 3 gets into contact with the model 18, a comparisoncircuit 23 detects that the difference signal Δε is zero, and providesan approach end signal AE to a data input device 37. When the processor24 reads the approach end signal AE and recognizes the completion ofapproach, tracing is started.

Upon starting of tracing, the processor 24 reads mode, referencedisplacement, tracing direction and the tracing velocity data, startingtracer control. The reference displacement data is converted by the D/Aconverter 10 into an analog reference displacement signal ε₀, which isapplied to the adder 9, and the X-axis servo motor 4 is driven in adirection based on the tracing direction data. By counting output pulsesfrom position sensors 29 to 31 which are mounted on the servo motors 4to 6, the current position of the machine (i.e. the current position ofthe stylus 3) is detected in reversible counters 32 to 34. The processor24 compares the contents of the reversible counters with the tracingstroke limits LP and IN stored in the memory 23 and controls the tracingrange. The control of the tracing range can be changed according to themanner of actuation of a sequence switching push button provided on acontrol panel 35, and this will hereinbelow be described for each case.

(1) When the sequence switching push button is not used (see FIGS. 5(a)and (d)):

For example, during tracing in a-(minus) direction, when the content ofthe X-axis reversible counter 32 reaches the tracing stroke limit IN, anaxis changeover takes place and the processor 24 reads data on the pickfeed direction, the pick feed value P and the pick feed speed andcontrols a pick feed. When the content of the Y-axis reversible counter33 becomes equal to the tracing stroke limit LP, the processor 24 makesthe stylus perform tracing in the opposite direction, that is, in a+(plus) direction. Further, the processor 24 reads a tracing endposition LTB and decides whether or not the stylus has reached the endposition during the pick feed, and when it is detected that the stylushas reached the end position, the processor reads automatic return,automatic return speed and automatic return position LRP data from thememory 23, and based on the fact that the automatic return is ON, itdrives the Z-axis servo motor 6. When the content of the reversiblecounter 32 reaches the automatic return position LRP, the tracer controlends.

(2) When the sequence switching push button is used:

Upon pressing the sequence switching push button 36 of the control panel35, an interrupt signal INT1 is sent to the processor 24. The processor24 executes an interrupt process shown in FIG. 5(b), after which it setsa flag A set in the memory 23 or the like and returns to the formerprocess. When the sequence switching push button 36 is released, aninterrupt signal INT2 is sent to the processor 24. The processor 24performs an interrupt process shown in FIG. 5(c) and in this process itresets the flag A and sets a flag B set in the memory 23 or the like.

Accordingly, when the push button 36 is pressed, for example, duringtracing in the -direction, since the flag A is set, even if the contentof the X-axis reversible counter 32 reaches the tracing stroke limit IN,no axis changeover takes place and tracing in the -direction iscontinued, as shown in FIG. 5(a). That is, tracing is continued beyondthe predetermined tracing range. Then, when the push button 36 isreleased, since the flag B is set, an axis changeover is immediatelycarried out and the processor 24 makes the stylus perform tracing in theopposite direction, that is, in the +(plus) direction. Further, even ifthe push button 36 is pressed before tracing gets beyond the tracingrange, an axis changeover immediately takes place similarly.Incidentally, the flag B is reset after the axis changeover.

In the interruption processing shown in FIG. 5(c), if a limit positionchangeover switch 40 provided on the control panel 35 is in the ON stateto hold a limit change mode, then the machine position at the moment ofrelease of the push button 36 is read and, in the case where the currenttracing is in the +direction, the tracing stroke limit X₂ is rewrittenwith the X position of the read machine position, while in the case of-direction tracing, the tracing stroke limit position X₁ is rewrittenwith the read X position of the machine position. Consequently, thesubsequent tracing range is defined by the corrected tracing strokelimit.

While the above embodiment is an application of the present invention toforward/reverse scan tracing, the invention is applicable, of course, toother kinds of tracing as well. Moreover, the present invention is alsoapplicable to such a system that the tracing range is defined by aplurality of coordinate values, for example, the tracing stroke limit isx₁ within a range of 0 ≦y ≦α and x₂ within a range α≦y≦β. In such acase, the change of the tracing stroke limit in the processing of FIG.5(c) is effected for each of the above ranges.

Furthermore, the present invention is applicable to a system in whichthe tracing range is defined by a limit switch. In this case, however,the change of the tracing stroke limit in FIG. 5(c) is impossible.

As described above, according to the present invention, it is possibleto ignore and resume a tracing sequence changeover by actuation of anexternally provided control switch whether within or without the tracingrange preset as store data of a limit switch or memory. Accordingly, thepresent invention provides greater freedom in modifying the tracingrange, offering the advantage of greater ease in initial setting of thetracing range. Further, since the present invention makes it possible toselectively ignore a sequence changeover and execute the ignoredsequence changeover with the use of one control switch in such a manneras to ignore a sequence changeover from the beginning of actuation(turning ON) of the control switch and to resume a sequence changeoverwhich has been or is to be ignored when the operation of the controlswitch is released (turned OFF), the number of parts used can be reducedas compared with that in such a system that uses one switch to ignore asequence changeover and another switch to execute the ignored sequencechangeover.

We claim:
 1. A sequence switching system in a tracer control unit whichoperates to provide a tracing direction and a tracing speed based onsignals from a tracer head tracing the surface of a model and performstracer control, comprising a control switch for inputting a sequenceswitching signal, a sequence changeover ignore means for ignoring thecurrent sequence changeover during actuation of the control switch, anda sequence changeover execute means for executing the sequencechangeover which as been or is to be ignored when the operation of thecontrol switch is released.
 2. A tracer control system comprisingcontrolmeans for operating a tracer for tracing a tracer head with respect to amodel over a tracing range, including for providing changeover sequencesbetween respective successive pairs of operations of said tracing oversaid range, and a control switch which can be engaged and released,responsive to said control means, for modifying the position at whichsaid changeover sequence between respective pairs of said operationsoccurs, wherein said control means operates such that when said controlswitch is engaged prior to when said tracer head reaches a respectivelimit of said tracing range at which said changeover sequence is tooccur, (1) if said control switch is released prior to said tracer headreaching said respective limit, the changeover sequence that otherwisewould next occur at the respective limit instead occurs at therespective position of the tracer head at the time of release, and, (2)if said control switch is released after said tracer head reaches saidrespective limit, said tracer head continues beyond said limit withoutany changeover sequence occurring until said control switch is released.3. The system of claim 2, wherein the respective position at which saidcontrol switch is released becomes the respective position limit forsubsequent tracing of said model.
 4. The system of claim 2, wherein thetwo respective operations between which said changeover sequence occursare a tracing operation and a following pick feed operation.
 5. Thesystem of claim 3, wherein the two respective operations between whichsaid changeover sequence occurs are a tracing operation and a followingpick feed operation.